Getting to know the transformer clamp ammeter
Structure and principle
A clamp meter is essentially composed of a current transformer, a clamp wrench, and a rectifier magneto electric system reactive force instrument.
The working principle of a clamp type meter is the same as that of a transformer. The primary coil is a wire that passes through a clamp type iron core, which is equivalent to the primary coil of a 1-turn transformer. This is a step-up transformer. The secondary coil and the ammeter used for measurement form the secondary circuit. When there is AC current passing through the wire, it is the alternating magnetic field generated by this coil, which induces current in the secondary circuit. The magnitude of the current is proportional to the proportion of the primary current, which is equivalent to the inverse ratio of the number of turns in the primary and secondary coils. A clamp type ammeter is used to measure large currents. If the current is not large enough, the number of turns of a wire passing through the clamp type ammeter can be increased, and the measured current can be divided by the number of turns.
The secondary winding of the through core current transformer of the clamp ammeter is wound around the iron core and connected to the AC ammeter. Its primary winding is the measured wire passing through the center of the transformer. The knob is actually a range selection switch, and the function of the wrench is to open and close the movable part of the core of the through core transformer, so as to clamp it onto the measured wire.
When measuring the current, press the wrench, open the pliers, and place the measured current carrying wire in the middle of the through type current transformer. When there is alternating current passing through the measured wire, the magnetic flux of the alternating current induces a current in the secondary winding of the transformer. This current passes through the coil of the electromagnetic ammeter, causing the pointer to deflect and indicating the measured current value on the dial scale.
After inserting the tested wire into the window through the iron core button, it is important to ensure that the two sides of the clamp have a good fit and that no other objects are placed in the middle;
The z-range of the clamp meter is 5A, and when measuring a small current, the display error will be larger. This can be measured by winding the energized wire on a clamp meter for a few turns, and the obtained reading value is divided by the number of turns to obtain the desired result.
Usage
(1) Mechanical zeroing is required before measurement
(2) Choose the appropriate range, first choose the large range, then choose the small range or estimate the nameplate value.
(3) When using a small range measurement with z, if the reading is not yet clear, the measured wire can be wound a few turns. The number of turns should be based on the number of turns in the center of the clamp, and the reading=indicated value x range/full deviation x number of turns
(4) After the measurement is completed, place the transfer switch at a large range of z.
(5) When measuring, the measured wire should be placed in the center of the clamp and the clamp should be tightly closed to reduce errors.
matters needing attention
(1) The voltage of the tested circuit should be lower than the rated voltage of the clamp meter.
(2) When measuring the current of high-voltage lines, it is necessary to wear insulated gloves, insulated shoes, and stand on an insulated mat.
(3) The jaws must be tightly closed and cannot be changed range with electricity.
